This product comes with no guarantee that the metal ring/teeth will not break similar to what may be the reason you are seeking a replacement.
This part is for use with the Updated Version of the Extruder / Feeder Mechanism.
- Monoprice MP Select Mini V2 - Check the product pictures to see if it matches what is on your printer
- Monoprice MP Mini Delta - Check the product pictures to see if it matches what is on your printer
Here are some printable replacement extruders/feeder mechanisms on Thingiverse - Thingiverse Collection of Extruders for the Mini Delta and Select Mini